Convert an image file readable by GDAL into a row-indexed text file

indexed_image.py

import numpy as np
from osgeo import gdal

def progress(n, interval=100):
    "Print progress at regular intervals"
    # don't want to divide by zero on first try
    if n > 0:
        if n % interval == 0:
            print "Parsing item %i" % n
    return

def image2indexed(fin, fout):
    """Convert image to text, with image row index as first element of each line."""
    print "\nLoading file %s" % fin
    fp = gdal.Open(fin)
    fp_out = open(fout, "w")
    arr = fp.ReadAsArray()
    
    print "Parsing file"
    for row in xrange(arr.shape[0]):
        # this will create a string of the array row
        line = " ".join(arr[row, :].astype(str).tolist())
        
        # this writes a line that starts with the row number
        fp_out.write(" ".join([str(row), line, "\n"]))

        progress(row)
    return